Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Porous graphene is considered to be a desirable membrane for gas separation. Theoretical and experimental studies indicate that atom-scale holes in the graphene lattice may provide significant selectivity for separating gases based on molecular size. Further, monolayer graphene, at one atom thick, is a desirable candidate because the gas permeation rate through a membrane increases with decreasing membrane thickness.
Consequently, porous graphene membranes are being pursued for their potential to significantly outperform conventional polymeric membranes, e.g., in separating gases that are synthesized at high temperatures. For example, the “shift reaction” used to create hydrogen gas from water and carbon dioxide may run at temperatures over 400° C. Since there is currently no membrane that effectively purifies hydrogen in a single operation, much less at such high temperatures, current hydrogen purification may include capital and energy intensive operations such as cooling, as well as removal of water, carbon dioxide, and other impurities.
A graphene membrane with uniformly sized pores may effectively purify hydrogen from the “shift reaction” in a single operation. However, although porous graphene has shown interesting performance in small-scale academic studies, current preparation methods are not capable of preparing a graphene membrane with uniformly sized pores. Known porous graphene examples have been created using a physical process such as electron or ion beams to damage the graphene surface, followed by oxidative expansion of the defects to create pores. Such methods have created porous graphene membranes with pores that vary significantly in size and in areal density over the membrane.
The present disclosure appreciates that preparing porous graphene, e.g., for use in separation membranes, may be a complex undertaking.